Doesn't pgstat_report_wal() handle the argument "force" incorrectly

Ryoga Yoshida <bt23yoshidar@oss.nttdata.com>

From: Ryoga Yoshida <bt23yoshidar@oss.nttdata.com>
To: pgsql-hackers@lists.postgresql.org
Date: 2023-09-22T04:58:37Z
Lists: pgsql-hackers
Hi,

pgstat_report_wal() calls pgstat_flush_wal() and pgstat_flush_io(). When 
calling them, pgstat_report_wal() specifies its argument "force" as the 
argument of them, as follows. But according to the code of 
pgstat_flush_wal() and pgstat_flush_io(), their argument is "nowait" and 
its meaning seems the opposite of "force". This means that, even when 
checkpointer etc calls pgstat_report_wal() with force=true to forcibly 
flush the statistics, pgstat_flush_wal() and pgstat_flush_io() skip 
flushing the statistics if they fail to acquire the lock immediately 
because they are called with nowait=true. This seems unexpected behavior 
and a bug.
void
pgstat_report_wal(bool force)
{
	pgstat_flush_wal(force);

	pgstat_flush_io(force);
}

BTW, pgstat_report_stat() treats "nowait" and "force" as the opposite 
one, as follows.
/* don't wait for lock acquisition when !force */
nowait = !force;

Ryoga Yoshida



Commits

  1. Fix behavior of "force" in pgstat_report_wal()